The present invention relates to prosthetic devices and, more particularly, to a knee joint assembly for an above knee prosthesis that has a significantly large surface contact area between the two half members of the knee joint assembly to distribute the load and stress forces across a large surface area in order to reduce the wear of the knee joint assembly.
Prior knee joint assemblies have been manufactured in metal and are generally comprised of two half members pivotally mounted to each other. Usually a locking pin assembly is utilized to lock the two halves together. In some prior devices, attached to one half member are two plastic discshaped pucks. The pucks are attached very near the locking pin and engage the base of the other half member when the two halves are locked together. However, only a small portion of each puck circumference engages the base.
When a person walks or stands while wearing the above knee prosthesis, the stress and load forces are transferred through the prosthesis to the knee joint assembly and specifically to the area of contact between the two half members. Of course, the two halves are locked to each other during these types of activities. Therefore, the load and stress forces are transferred to the puck circumference area which engages the base. After a period of time this causes the puck circumference area to deform which allows movement between the two half members even when they are locked together. This causes instability of the prosthesis. Therefore, the person will then either obtain a new prosthesis or knee joint assembly, or continue using the prosthesis, thereby jeopardizing his or her safety.
People in third world countries who require above knee prostheses need a prosthesis which will last long, is inexpensive, can be adjusted immediately, and is lightweight. Additionally, since these people usually perform more manual labor than others, the stress and load forces applied to the prosthesis is increased. Therefore, the prosthesis will become unstable sooner and since these people usually are very poor, they will continue to use the unsafe prosthesis. Furthermore, since many of these people live in remote areas or where clinics and hospitals are far, they need a prosthesis which can be adjusted for them where they are located.
The present invention is a knee joint assembly which is lightweight and provides a substantially larger area of surface contact between the two half members. This increases the distribution of load and stress forces, thereby reducing the wear and increasing the longevity of the knee joint assembly.